Sustainable synthesis of branched-chain diesters

Recent advances and future prospects for biolubricant base stocks production using lipases as environmentally friendly catalysts: a mini-review

In recent years, fluctuating global fossil fuel market prices and growing concern about environmental pollution have increased efforts to obtain novel value-added products from renewable agricultural biomass. To this end, a wide variety of triacylglycerols (edible and non-edible oils and fats) and their derivatives (free fatty acids or monoalkyl esters) stand out as promising feedstocks for the production of biolubricant base stocks, due to their biodegradability, excellent physicochemical properties, and sustainable nature. These raw materials can be transformed into biolubricants using chemical or biochemical (lipases) catalysts, with the enzymatic production of biolubricants using lipases as catalysts being recognized as an environmentally friendly approach. The present mini-review highlights recent advances in this field, published in the last three years. The different chemical modification processes used to develop a wide variety of industrial biolubricant base stocks are comprehensively reviewed, with exploration of future prospects for industrial production via the enzymatic route. This study contributes to the current state-of-the-art, identifying relevant research questions and providing important technical information for new applications of lipases in oleochemical manufacturing industries.

Sustainable Biocatalytic Procedure for Obtaining New Branched Acid Esters

Biocatalytic synthesis of 2-ethylhexyl 2-methylhexanoate is described in this work for the first time. This branched-chain ester is suitable for use at low temperatures in numerous applications. The immobilized lipase Novozym® 435 has demonstrated its ability to catalyze the ester synthesis from 2-ethylhexanol and 2-methylhexanoic acid in a solvent-free medium. The high reaction times that are required result in a loss of alcohol by evaporation, which must be compensated for with an excess of this substrate if high conversions are to be achieved. Therefore, two strategies are established: 70 °C with a 10% excess of alcohol, which requires a longer operating time and provides conversions of 97%, and 80 °C with a 20% excess of alcohol, which allows for the achievement of a 99% conversion in a shorter time. The optimal reaction conditions have been chosen based on reusability of the enzyme, process productivity, green metrics and preliminary economic study. When the synthesis is carried out under the best conditions (70 °C, 10% molar excess of alcohol and six uses of the immobilized enzyme) a productivity of 203.84 kg product × kg biocatalyst-1 is attained. The biocatalytic procedure matches many of the objectives of "green chemistry" and is suitable to be scaled up and used in industrial manufacturing.